1. Field of the Invention
The present invention relates to a semiconductor device having an insulated gate structure using a crystalline silicon film disposed on an insulating substrate of glass, quartz or the like, for example, a thin film transistor (TFT), a thin film diode (TFD), and a thin film integrated circuit using the thin film elements, especially a thin film integrated circuit for a passive matrix type liquid crystal display device and a thin film integrated circuit for an active matrix type liquid crystal display device, and also relates to a method of manufacturing the same.
2. Description of the Related Art
In recent years, there has been vigorously carried out studies on an active matrix type liquid crystal display device in which thin film transistors are formed in a matrix form on an insulating substrate of glass, quartz or the like, and the TFTs are used as switching elements.
Also, an attention has been paid to an active matrix type liquid crystal display device in which an active matrix circuit (also called a pixel circuit or pixel matrix circuit) and a peripheral drive circuit (also called a driver circuit) are integrated on the same insulating substrate. This structure is called a peripheral drive circuit integration type.
A conventional active matrix type liquid crystal display device uses transparent electrodes in which electrodes for driving a liquid crystal layer are formed on two substrates faced to each other. A liquid crystal is sealed between the two substrates, and the direction of an electric field applied to the liquid crystal is made substantially perpendicular to the surface of the substrate. The liquid crystal device is realized by changing the intensity of the electric field so that the direction of orientation of liquid crystal molecules generally having a rod shape are changed so as to be parallel to the substrate or perpendicular to the substrate. Generally, in this case, since light is made to be modulated by using an optical anisotropy as one of features of the liquid crystal material, a polarizing plate is disposed in the device so that incident light is made linearly polarized light.
However, in the liquid crystal electro-optical device having such an operation method, there is observed such a phenomenon that although the state of display is normal when the display surface is seen from the direction perpendicular thereto, the display is dark and becomes blurred when the display surface is seen from the direction at an angle thereto, and further, color is changed when the display is colored.
In order to solve such a problem, there is a method (IPS mode) in which the direction of an electric field applied to a liquid crystal layer is made parallel to the surface of a substrate.
In such an electro-optical device, since switching is carried out while a longitudinal axis of a liquid crystal molecule is kept parallel to the substrates, the change of optical characteristics of the liquid crystal due to an angle of visual field is small.
Thus, leak of light, lowering of contrast and the like due to the angle of visual field are smaller than a conventional TN or STN system.
There is known a structure of an electrode of this IPS mode as shown in FIG. 17 in which a comb-shaped electrode is formed on one substrate.
However, there is a problem that when the comb-shaped electrode is used, a wiring pattern is made minute and complicated in a pixel element, so that productivity becomes inferior.
Also, since the shape of the electrode is complicated, an electric field applied to a liquid crystal layer becomes complicated.
Further, light is shaded by the comb-shaped electrode, so that an effective area (opening rate) through which light can passes, becomes extremely low. Thus, only a dark display can be realized, and it can not be put into practical use.
The present invention has been made to overcome the above described problems, and an object of the invention is therefore to provide a liquid crystal display device of peripheral drive circuit integration type which has high contrast even if a transparent electrode is not provided, can be manufactured through simple steps, can be mass-produced, has a large opening rate, and is bright. Another object thereof is to provide a method of manufacturing the same.
In order to solve the above problems, according to the present invention, the following means are adopted.
According to a first aspect of the present invention, as shown in FIG. 1, a liquid crystal display device is characterized by comprising: a pair of substrates, at least one thereof being transparent; a liquid crystal layer placed between the pair of substrates; a plurality of pixels arranged in a matrix form on one thereof; a pixel electrode 108 and common electrodes 110 and 111 existing in the same layer; and common lines 103 and 104 existing in a layer different from the common electrodes through an insulating layer and being connected to the common electrodes through contact holes, an electric field being applied between the pixel electrode and the common electrodes substantially parallel to the surface of the substrate so as to control the state of orientation of liquid crystal molecules so that light can be modulated.
In the above structure, the liquid crystal display device is an active matrix type liquid crystal display device in which a thin film transistor is disposed for each of the pixels, and the thin film transistor includes a pixel electrode 108, gate lines 102 and 105 connected to a scanning line, and source lines 106 and 107 connected to a signal line.
In the above structure, the liquid crystal display device is a passive matrix type liquid crystal display device driven in a passive manner.
In the liquid crystal display device, the common electrodes 110 and 111, and the pixel electrode 108 are parallel to each other, exist in the same layer as shown in FIG. 2, and are made of the same material and by the same steps.
In the liquid crystal display device, the common electrodes and the pixel electrode are made of aluminum, metal mainly containing aluminum, silicon, or a laminated layer of titanium and aluminum.
In the liquid crystal display device, the common lines 103 and 104 and the gate lines 102 and 105 exist in the same layer as shown in FIG. 2, and are made of the same material and by the same steps.
According to a second aspect of the present invention, as shown in FIG. 3, a liquid crystal display device is characterized by comprising: a pair of substrates, at least one thereof being transparent; a liquid crystal layer placed between the pair of substrates; a plurality of pixels arranged in a matrix form on one thereof; a pixel electrode 108 and common electrodes 110 and 111 existing in the same layer; a common line existing in a layer different from the common electrodes through an insulating layer and being connected to the common electrodes through contact holes; and a flattened film 230 disposed on the common electrodes and the pixel electrode, an electric field being applied between the pixel electrode and the common electrodes substantially parallel to the surface of the substrate so as to control the state of orientation of liquid crystal molecules, so that light can be modulated.
In the liquid crystal display device, the flattened film 230 disposed on the common electrodes and the pixel electrode is formed of an organic material film made of polyimide or the like, an inorganic material film made of silicon nitride, silicon oxide or the like, or a laminated film thereof.
Also, as shown in FIG. 1, a liquid crystal display device is characterized by comprising: a pair of substrates, at least one thereof being transparent; a liquid crystal layer placed between the pair of substrates; a plurality of pixels arranged in a matrix form on one thereof; and a pixel electrode 108 placed between a pair of common electrodes 110 and 111 in one pixel, an electric field being applied between the pixel electrode and the common electrodes substantially parallel to the surface of the substrate so as to control the state of orientation of liquid crystal molecules, so that light can be modulated.
According to a third aspect of the present invention, as shown in FIGS. 4 to 8, a method of manufacturing a liquid crystal display device is characterized by comprising the steps of: forming a crystalline semiconductor layer 101 on a substrate having an insulating surface 201; forming a gate insulating film 205 on the crystalline semiconductor layer; forming a first conductive film 210 on the gate insulating film; shaping the first conductive film into gate lines 102 and 105, and common lines 103 and 104; doping the crystalline semiconductor layer; forming a first interlayer film 206 on the entire surface; forming contact holes; forming a second conductive film on the first interlayer film; and shaping the second conductive film into a pixel electrode 108, common electrodes 110 and 111, and source lines 106 and 107.
The crystalline semiconductor layer in the present invention is a silicon film having at least crystallinity, such as a single crystal silicon film, a polycrystalline silicon film containing both amorphous silicon and crystal silicon, and a polycrystalline silicon film mainly composed of amorphous silicon and containing a slight amount of crystalline silicon.
In order to obtain a structure as shown in FIG. 3, a method of manufacturing a liquid crystal display device is characterized by comprising the steps of: forming a crystalline semiconductor layer 101 on a substrate having an insulating surface 201; forming a gate insulating film 205 on the crystalline semiconductor layer; forming a first conductive film 210 on the gate insulating film; shaping the first conductive film into a gate line 105, and common lines 103 and 104; doping the crystalline semiconductor layer; forming a first interlayer film 206 on the entire surface; forming contact holes; forming a second conductive film on the first interlayer film; shaping the second conductive film into a pixel electrode 108, common electrodes 110 and 111, and source lines 106 and 107; and forming a flattened film 230 on the pixel electrode, the common electrodes, the source lines, and the entire surface of the substrate.
A method of manufacturing a liquid crystal display device is characterized by comprising the steps of: forming a crystalline semiconductor layer on a substrate having an insulating surface; forming a gate insulating film on the crystalline semiconductor layer; forming a first conductive film on the gate insulating film; shaping the first conductive film into a gate line and a common line; doping the crystalline semiconductor layer; forming a first interlayer film on the entire surface; forming contact holes; forming a second conductive film on the first interlayer film; and shaping the second conductive film into a pixel electrode, a common electrode, and a source line, wherein five or less masks are used in the manufacturing steps.
In the method of manufacturing a liquid crystal display device, the flattened film 230 on the common electrode is formed of an organic film of polyimide or the like, an inorganic material film of silicon nitride, or a laminated film thereof.
A method of manufacturing a liquid crystal display device is characterized by comprising the steps of: forming a crystalline semiconductor layer on a substrate having an insulating surface; forming a gate insulating film on the crystalline semiconductor layer; forming a first conductive film on the gate insulating film; shaping the first conductive film into a gate line and a common line; oxidizing the first conductive film; carrying out first impurity doping to the crystalline semiconductor layer; removing the oxidized conductive film; carrying out second impurity doping with concentration lower than the first impurity doping after the step of removing the oxidized conductive film; forming a first interlayer film on the entire surface; forming a contact hole; forming a second conductive film on the first interlayer film; and shaping the second conductive film into a pixel electrode, a common electrode, and a source line, wherein five or less masks are used in the manufacturing steps.
The above method further comprises a step of forming a flattened film on the entire surface of the substrate after the step of shaping the second conductive film into the pixel electrode, the common electrode and the source line, wherein five or less masks are used in all the manufacturing steps.
According to a fourth aspect of the present invention, as shown in FIG. 9, a liquid crystal display device is characterized in that a wiring connection terminal 900 for an external device is made of a laminated layer which is formed by lamination of at least two wiring lines.
As shown in FIG. 10B, a liquid crystal display device is characterized in that a wiring connection terminal 900 for an external device is made of a laminated layer of at least two wiring lines, which is disposed on a silicon film 101 formed on an insulating substrate.
In the liquid crystal display device, the laminated layer of wiring lines is formed of the same material and by the same step.
In the liquid crystal display device, the wiring connection terminal 900 is made of aluminum, metal mainly containing aluminum, conductive inorganic compound, silicon, or a laminated layer of titanium and aluminum.
As shown in FIG. 10B, a method of manufacturing a liquid crystal display device is characterized by comprising the steps of: forming a first conductive film 210 on a substrate 201 having an insulating surface; shaping the first conductive film into a first wiring terminal 211; forming a second conductive film 220 on the first conductive film; shaping the second conductive film into a second wiring terminal 221; forming an interlayer insulating film 230 on the entire surface of the substrate; and shaving off the interlayer insulating film on the surface of the substrate to expose the upper surface of the second wiring terminal to form a wiring connection terminal 900 for an external device.
A method of manufacturing a liquid crystal display device is characterized by comprising the steps of: forming a semiconductor layer 101 on a substrate 201 having an insulating surface; forming a first conductive film 210 on the semiconductor layer; shaping the first conductive film into a first wiring terminal 211; forming a second conductive film on the first conductive film; shaping the second conductive film into a second wiring terminal 221; forming an interlayer insulating film 230 on the entire surface of the substrate; and shaving off the interlayer insulating film on the surface of the substrate to expose the upper surface of the second wiring terminal to form a wiring connection terminal 900 for an external device.
According to a fifth aspect of the present invention, as shown in FIG. 12, a liquid crystal display device is characterized by comprising: a pair of substrates, at least one being transparent; a liquid crystal layer placed between the pair of substrates; first wiring lines and second wiring lines existing in layers different from each other through an insulating layer, the second wiring lines shading a region between the first wiring lines adjacent in parallel to each other, and the first wiring lines shading a region between the second wiring lines adjacent in parallel to each other; and pixel display regions surrounded by the first wiring lines and the second wiring lines, the pixel display regions being able to modulate light.
A liquid crystal display device is characterized by comprising: a pair of substrates, at least one being transparent; a liquid crystal layer placed between the pair of substrates; a pixel electrode 1208 placed between a pair of common electrodes 1210 and 1211 in one pixel; a common line 1203 shading regions between the source lines 1206 and 1207 and the adjacent common electrodes; and a pixel electrode 1208 shading a region between a gate line 1205 and the adjacent common line 1203.
In the liquid crystal display device, holding capacitance is formed between both the common line 1203 and gate line 1205 of the first wiring line and the pixel electrode of the second wiring line.
As shown in FIG. 16, a liquid crystal display device is characterized in that an opposite substrate includes a plurality of black matrices 1600 smaller than a common electrode 1210 so that they sufficiently cover gaps occurring between wiring lines when the pair of substrates are laminated.